Field of the Invention
The present invention relates to a method of producing a liquid developer for use in an image-forming apparatus that utilizes an electrophotographic system, e.g., electrophotography, electrostatic recording, electrostatic printing, and so forth.
Description of the Related Art
Plate-based presses have in the past been used to produce printed material for which a certain number of copies are required, such as regional advertising, internally distributed business documents, and large posters. In place of these conventional presses, on-demand presses have entered into use in recent years; these on-demand presses can rapidly respond to a diversifying range of needs and support inventory reductions. Electrophotographic printers that use a dry developer or a liquid developer and inkjet printers capable of high speeds and high quality printing are anticipated for such on-demand printers.
Dry developers currently occupy the developer mainstream due to their handling advantages, which derive from the fact that a solid developer is being handled. However, viewed from the standpoint of preventing the image deterioration caused by changes in the environment, e.g., temperature and humidity, the environmental stability of the charging performance has been a problem with dry developers. In addition, the colored resin particles in a dry developer readily undergo aggregation during, for example, storage, and uniformity when the colored resin particles are dispersed has been a problem. In addition, with regard to their properties, when the colored resin particle diameter is made relatively small in pursuit of high resolution, the problems deriving from the fact that the dry developer is in the form of powder is involved as described above become even more substantial.
Liquid developers, on the other hand, use an electrically insulating liquid as a carrier liquid and because of this are more resistant than dry developers to the problem of aggregation of the colored resin particles in the liquid developer during storage, and a microfine toner can thus be used. As a result, liquid developers provide a better fine line image reproducibility and a better gradation reproducibility than dry developers and are characterized by an excellent color reproducibility and also excellence in high-speed image-forming methods. Development is becoming quite active with regard to high-image-quality, high-speed digital printing apparatuses that exploit these excellent features by utilizing electrophotographic technologies that use liquid developers. In view of these circumstances, there is demand for the development of liquid developers that have even better properties.
Japanese Patent No. 4,977,034 discloses a liquid developer that is produced using the coacervation method and that has colored resin particles containing an acid group-bearing resin having an acid value of 1 to 100 dispersed in an insulating hydrocarbon-type dispersion medium.